The background of the invention will be discussed in two parts.
1. Field of the Invention
This invention relates to microscopes and more particularly to a microscope for performing surgery on the eye.
2. Description of the Prior Art
With ophthalmic surgery, for example, surgery involving cataracts, ideally it is desirable to reconfigure the cornea after the operation to the same radius of curvature existing prior to the operation. In the human eye, the radius of curvature varies from individual to individual with a normal range being between 40 and 50 diopters which correspond to radii of curvature of 8.44 millimeters to 6.75 millimeters, respectively. In order to ascertain the radius of curvature prior to the operation, measurements are taken along certain angles or meridians. Heretofore, such measurements have been taken by means of telescopic instruments known as ophthalmometers or Keratometers. A corneal measurement technique is shown and described in U.S. Pat. No. 3,895,860 and a Keratometer device is referred to in U.S. Pat. No. 3,972,602.
In measuring the size or radius of curvature of the cornea, the instrument heretofore used is the Keratometer or opthalmometer. Such a device is a monocular device, and in one embodiment a telescope is utilized, the telescope having an optical axis in alignment with the cornea to be measured. Mires, or illuminated targets, have the reflections thereof seen in the cornea through the telescope system. The mires generally are arranged in some manner, such as on a track whereby they can be moved toward each other or further away by rotation of a dial or the like. The image of the mires passes through condensing lenses and then through a diaphragm with four apertures. The light continues through two of the apertures without deviation. A doubling system, consisting of two adjacent prisms have one of the prisms arranged for horizontal displacement and the other for vertical displacement. Each of the prisms is placed before one of the remaining apertures resulting in four different images. The two images which are not affected by the prisms are utilized to place the instrument in proper focus much as in the manner of the coincidence range finder, that is, when the two non-affected images are coincident, the instrument is in proper focus. The focusing is accomplished by suitable adjustment of the telescope device. With two of the images coincident, upon viewing through the telescope, only three images are then seen, with a first image being in a given location, a second image in vertical alignment therewith and the third image in horizontal alignment therewith. The two doubling prisms can then be moved independently of each other to place the three images in proper alignment with each other. Since the power of each of the prisms is known, the displacement of the images can be calibrated according to the position of the prisms to determine the radius and curvature of the cornea.
The Keratometer and other similar opthalmometers utilize the same principles and have the same essential parts. Each device has an object an area bounded by the mires, which are the transluscent illuminated targets reflected by the cornea. Such instruments have a telescope for focusing the catoptric images of the mires and means for placing the images in the focal plane of the objective lens of the telescope for clearer surveyance. The examiner, or user of the instrument, must focus the hairlines within the telescope by moving the ocular lens of the telescope. At this focuses the image of the hairline in the focal plane of the objective lens, the telescope is arranged for precise observation of the images from the cornea. Such instruments also possess a doubling system which separates the images to an extent which equals the size of the images when their borders are touching. The extent of displacement is known for given positions of the prisms.
However, as a tool or instrument useful in the performance of surgery on the eye, such Keratometers and optalmometers are not suitable inasmuch as the image seen by the examiner is upside down and backwards. Additionally, the device is bulky and the monocular nature of the instrument precludes depth perception. Furthermore, measurement of radius of curvature of the cornea utilizing monocular opthalmometers or Keratometers are generally accomplished in a darkened room in order to eliminate background lighting which would hinder obtaining of the desired measurements.
An operating microscope for ophthalmic surgery is currently being manufactured and sold by Edward Weck & Company, Inc. of Long Island City, N.Y., the microscope utilizing a fibre optic light source to illuminate a circle of twelve pinpoint lights which are reflected from the cornea and superimposed within concentric rings of the eyepiece reticle during suturing of the cornea to enable the surgeon to determine when a spherical surface of the cornea has been achieved, the configuration of the reflected lights and the positioning within the appropriate concentric ring being indicative of the corneal size.
With the radius of curvature of the cornea determined prior to the operation, the surgeon attempts to reconstruct this radius after the operation. When an operation such as a cataract operation is performed, an incision is made in the Limbus or periphery of the cornea about an arc of approximately 180.degree. of the periphery. The fluid within the anterior chamber is removed and the lens of the eye is then removed. In some instances, the lens is replaced utilizing known plastic lens implantation techniques, but in either event after the lens removal and the implantation, if performed, a saline solution is inserted into the anterior chamber and the corneal incision is then sutured. Ideally, the sutures are tensioned by the surgeon to provide the same configuration of the cornea that existed prior to the operation, that is, having the same radius of curvature. Binocular surgical microscopes are utilized in the performance of this operation to magnify the cornea to enable the delicate operation to be performed. However, even with the surgical microscope hereinabove described, the reconstruction of the corneal configuration by suitably tensioning the sutures is still very much a function of the skill of the hands and eyes of the surgeon performing the operation.
It is accordingly an object of this invention to provide a new and improved surgical microscope system.
It is another object of this invention to provide a new and improved surgical microscope system for use in an operation of the eye.
It is a further object of this invention to provide a method for utilizing the microscope as a surgical tool to reconfigure the cornea to its pre-operative condition or to reconfigure the cornea to rectify other eye disorders.